Wind Turbine Blades Made of Functional Materials

Omoware, Wisdom (2017) Wind Turbine Blades Made of Functional Materials. Doctoral thesis, Northumbria University.

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Abstract

Blades are designed to have good rigidity to be able to minimise the destruction that could be caused by rapid wind load and gust. The increase in length of the wind turbine contributes to the susceptibility of the wind turbine blade to the unpredictable destruction caused by random gusts. One of the ways to effectively increase the blade flexibility as well as increase its unloading effect led to the focus of this research on adaptive wind turbine blades. The project aims to investigate the potential benefits of flapping blades in the extraction of wind energy and proposing an analytical model for the prediction of the normalised induced twist with the sole purpose of having a robust tool for optimal design of adaptive wind turbine blades. In order to achieve these goals, the project is carried out in two aspects. Firstly, a proof of concept of a flapping blade; this report presents the preliminary results of the numerical simulation of a flapping-pitching rectangular flat plate in a uniform air flow. Various combinations of flapping amplitude, flapping frequency and pitching amplitude are analysed and their effect on the instantaneous and maximum lift coefficient is presented. The change in the flapping frequency and amplitude were shown to have considerable effect on the lift coefficient. It can be deduced from the results that the lift coefficient is influenced by the flapping frequency and flapping amplitude combination. The lift coefficient is most affected by the flapping amplitude when compared to the flapping frequency. The results indicate that the pitching amplitude initially enhances the lift coefficient. However, excessive pitching amplitude results in low lift coefficient.

The second aspect is to develop a robust analytical model for the prediction of the normalised induced twist of an adaptive blade. Wind turbine adaptive blade design is a coupled aero-structure (CAS) design process, in which, the aerodynamic performance evaluation requires structural deformation analysis of the adaptive blade. However, employing finite element analysis (FEA) based commercial packages for the structural deformation analysis as part of the aerodynamic objective evaluation process has been proven to be time consuming. In order to develop the robust tool for the prediction of the normalised induced twist, the effect of shell thickness distributions, fibre angle distributions and materials are investigated using arbitrary lay-ups configurations. The structural/material configurations and the analyses of the adaptive blades are performed using an auxiliary software tool developed via MATLAB codes for implementing structural deformation analysis. The results are generated in ANSYS Parametric Design Language (APDL), which are read using ANSYS for the extraction of the results. Static and dynamic analyses are carried out for several cases, and the results are used to develop the analytical model for the prediction of the normalised induced twist. The proposed analytical model performance is validated by comparing the normalised induced twist predicted using the proposed model with those obtained using the ANSYS and the results suggest that the proposed model is efficient in predicting the normalised induced twist of an adaptive blade.

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